Protractor



'Del. 3,1946.^ `NQSMWH f 2,412,100.

PROTRACTOR Filed Nov. 29. 1944 Patented Dec. 3, 1946 UNITED STATE yritoTnAoifoR V M Neil C. smith, Minneapolis, Minn.

" Appneaiion November 29,1944, serial No. 565,697

lt/ly'present invention relates vto improvements in protractors of thetype having a rotatable turret andra blade slidably mounted thereon.

The object of this invention isvto provide an extremelyisirnple andhighly eflicient protractor" having commonV means for simultaneouslylocking the'turret against rotation and the blade against slidingmovement.

Other objects vof the invention will be apparent fromthe followingdescription, reference :being had to the accompanying drawing.

3 To the above end, generally stated, the invention consists of thenovel devices andcombination of devices hereinafter described and denedin the claims.

In the accompanying drawingwhich illustrates the invention, likecharacters indicate like parts throughout the several views.

Referring to the drawing:

Fig. 1 is a plan View of the improved protractor;

Fig. 2 is a bottom plan View of the turret and the blade removed fromthe body of the protractor;

Fig. 3 is a fragmentary plan view of the body with the turret and theblade removed therefrom;

Fig. 4 is a view partly in side elevation and partly in section taken onthe line 4-4 of Fig. 1, on an enlarged scale;

Fig. 5 is a plan view of the Washer removed from the protractor, asshown in Fig. 4; and

Fig. 6 is a bottom plan View of the washer as shown in Fig. 5.

The numeral 'l indicates the body of the protractor which, as shown, isin the form of a blade, the longitudinal edges of which are parallel.One end portion of the body I is enlarged to afford a head 8. At thecenter of the head 8 is an upstanding tubular pivot 9, the lower endportion of which is reduced in diameter and mounted in a hole in saidhead. An annplar shoulder l is formed by reducing the lower end portionof the pivot 9 and which shoulder I0 rests directly on the head 8. Thelower end of the pivot 9 is upset within the plane of the body 'l torigidly secure the pivot 9 to the head 8 with its axis perpendicular tothe plane of the body 1. This method of securing the pivot 9 to the head8 leaves the bottom of the body 'l perfectly smooth so that said bodywill rest flat on a support.

A flat turret Il is mounted on the pivot 9 for rotation about the axisthereof in a plane parallel to the plane of the body Substantially 180degrees of the turret II is on the arc r vturret I I.

ofa circle having' its center at -the axis of said turret II. Thissection of the Aturret is -beveled to a relatively sharp edge at itsunderside,v as indicated at I2.

A thin narrow blade I3 is mounted in a channel I4 in the under side ofthe turret `for endwise sliding movement. This channel'M is in theopposite side of the turret |I from' the intermediate portion of thebevel I2. A springY member I5 in the channel I4, between one sidethereof and the adjacent longitudinal'edge "of the blade I3, yieldinglyholds said blade pressed against the other side of said channel wherebythe blade I3 is frictionally held where endwis'eadjusted in the channelI4. The spring'mem-` ber I5 is held in the channel I4 by a pin I6. Theblade I3 rests atwise directly on the head 8- and the central portion ofthe turret I I also rests directly on said head. Said turret l I, latits outer portion, has a working clearance with the body 1, see Fig. 4.

The longitudinal edge of the blade I3 that is in direct engagement withthe side of the channel I4 has dove-tailed engagement with the The upperend portion of the pivot 9 extends outwardly of the turret II and isreduced in diameter and diametrically opposite sides of this reducedportion are flattened, as indicated at Il. A washer I8 is mounted on thereduced outer end portion of the pivot 9 and the hole therein has thesame contour as the respective portion of the pivot 9 and is therebyheld from turning on the pivot 9. The under side of the Washer I8 isdished at I9 so that only its outer marginal portion bears on the turretI I.

A screw 20 extends into the tubular pivot 9 and has threaded engagementtherewith. This screw 20 has a large head 2|, the periphery of which isbeveled and knurled. On the under side of the screw head 2| is a thinhub 22 that bears directly on the washer I8.

Obviously, by tightening the screw 20, the turret II will befrictionally clamped onto the lbody 'l and thereby held against rotationand at the same time the blade I3 will be frictionally clamped ontothebody 'I and thereby held against endwise sliding movement. It will benoted that the screw head 2| extends outwardly of the washer I8 so thatthe same can be easily gripped with the ngers. The size of the screwhead 2| makes it very easy to manipulate. The turret II, the washer I8,the screw 20 and the screw head 2| all have their axis at the axis ofthe pivot which lends itself for accuracy and easy assembly. The washerI8, due to its dished under side, bears only on'its outer portion on theturret II. This structure gives an even pressure on the turret in acomplete circle that is concentric to the pivot 9, thereby holds theturret II in a plane that is parallel to the plane of the body 1 andprevents tilting thereof on the pivot 9 and thus prevents undue wear andstrain on said pivot.

By reference to Fig. 4 it will be noted that there is a workingclearance between the upper end of the pivot 9 and the hub 22. Thedished under side of the washer I8 affords a good working clearancebetween the shouldered upper end of the pivot 9 and said Washer and thesurface of the turret I I underlying said dished portion of the washerI8.

The body 1 and the blade I3 each Vhas Ythereon a scale of inches asindicated at 23 and 24, respectively. A circle, outward of the curvedportion of the turret II and having its center at the axis 4of the pivot9 is divided into quarters, and each quarter vgraduated into 90 degrees,Vas indicated at 25. These degrees read from two diametrically oppositezero points. Tw'o zero marks 26 and 21 are shown on the turret II spaced90 degrees apart for co-operation with the degree graduations 25. Bymeans of one of these zero points 25 and 26, the turret II may beadjusted to position the blade I3 at a required angle relative tothebody 1 and the degree reading at .the other zero point will give thecomponent angle. A Vernier scale 28 on the turret II has its zero pointat the zero point 21 and reads in opposite directions therefrom. Theclose proximity of the beveled edge of the turret II with the degreemarkings 25 lends itself to easy and accurate reading of said degrees.

vWhat I claim is:

1. In a device of .the class described, a body having an upstandingpivot, a turret turnably mounted on the pivot with freedom for axialmovement and resting on the body, a blade mounted on the turret forendwise sliding movement and resting on the body, a washer mounted onthe pivot with freedom for axial movement, held against relative turningmovement and resting on the turret, a member having threaded engagementwith the pivot and bearing on the washer and operable to simultaneouslyfrictionally clamp the turret onto the body and thereby hold the turretfrom turning on the pivot and frictionally clamp the blade between thebody and the turret and thereby hold the blade from sliding endwiserelative to the turret and the body.

2. In a device of the class described, a body 'having an upstandingtubular pivot, a turret turnably mounted on the pivot with freedom foraxial movement, resting on the body, and having a channel in itsl underside, a blade mounted in said channel for endwise sliding movement andresting on the body, a Washer mounted on the pivot with freedom foraxial movement, held against relative turning movement and resting onthe body, a thumb-screw having threaded engagement With the tubularpivot with its head bearing on the washer and operable to simultaneouslyfrictionally clamp the turret onto the body and thereby hold the turretfrom turning on the pivot and frictionally clamp the blade between thebody and the turret and hold the blade from sliding endwise relative tothe turret and the body.

3. The structure defined in claim 2 in which the Washer is dished on itsunderside and thereby engages the turret only at its perimeter.

NE1L C. SMITH.

